Methods and apparatus for analyzing high voltage circuit breakers

Abstract

Methods, computer program segment and apparatus for analyzing high voltage circuit breakers are provided. The method includes determining a circuit breaker contact closing time, determining a circuit breaker contact opening time, and determining a circuit breaker pre-insertion resistor resistance value using at least three voltage samples and three current samples to facilitate reducing an induced current measurement error. The computer program segment is embodied on a computer readable media and is programmed to determine a circuit breaker contact closing time, determine a circuit breaker contact opening time, and determine a circuit breaker pre-insertion resistor resistance value using at least three voltage samples and three current samples that facilitate minimizing an induced current measurement error. The apparatus includes a testing circuit, an overvoltage protection circuit, and a processor programmed to determine a circuit breaker contact timing measurement and a circuit breaker contact resistance measurement.

1. A method for measuring a resistance of an electrical contact pair in the presence of a low frequency electromagnetic interference wherein the contact pair includes at least one movable contact, the movable contact is movable to break electrical contact with the other contact during an open operation, and the movable contact is movable to make electrical contact with the other contact during a close operation, said method comprising:
 injecting a high frequency signal across a contact pair in an open state; 
 measuring a voltage across the contact pair; 
 measuring a current flowing through the contact pair; and 
 calculating a resistance of the contact pair using a measured voltage and a measured current sampled at a first time, a measured voltage and a measured current sampled at a second time, and a measured voltage and a measured current sampled at a third time to facilitate minimizing induced current measurement error wherein the first, second, and third times are spaced approximately one half period of the high frequency signal apart. 
 
   
   
     2. A method in accordance with  claim 1  further comprising:
 changing the state of the contact pair from the open state to a closed state; 
 measuring a voltage across the contact pair during the change of state; 
 measuring a current flowing through the contact pair during the change of state; and 
 calculating a resistance of the contact pair during the change of state using the measured voltage and the measured current. 
 
   
   
     3. A method in accordance with  claim 1  wherein injecting a high frequency signal comprises a square wave. 
   
   
     4. A method in accordance with  claim 1  wherein measuring comprises sampling the voltage across the contact pair and the current flowing through the contact pair at least a local minimum value, a first local maximum value occurring just prior to the local minimum in time, and a second local maximum occurring just subsequent to the local minimum in time. 
   
   
     5. A method in accordance with  claim 1  wherein calculating a resistance of the contact pair comprises calculating a resistance of the contact pair using the formula:
     R   n =( V   N −( V   N−1   +V   N+1 )/2)/( I   N −( I   N−1   +I   N+1 )/2); 
 where; 
 R n  is the resistance of the contact pair; 
 V N  is a local minimum magnitude of the injected and induced voltage signal; 
 V N −1  is a local maximum magnitude of the injected and induced voltage signal preceding the local minimum; 
 V N +1  is a local maximum magnitude of the injected and induced voltage signal succeeding the local minimum; 
 I N  is a local minimum magnitude of the injected and induced current signal; 
 I N−1  is a local maximum magnitude of the injected and induced current signal preceding the local minimum; and 
 I N+1  is a local maximum magnitude of the injected and induced current signal succeeding the local minimum. 
 
   
   
     6. A method for analyzing the operation of circuit breakers, said method comprising:
 injecting a voltage signal across a circuit breaker contact pair during a testing sequence; and 
 determining at least one of a circuit breaker pre-insertion resistor resistance value and a contact pair resistance using at least three voltage samples and three corresponding current samples to facilitate reducing an induced current measurement error wherein the samples are spaced apart approximately one half period of the voltage signal. 
 
   
   
     7. A method in accordance with  claim 6  further comprising:
 electrically coupling a voltage source to a circuit breaker line side connection; and 
 electrically coupling the voltage source to a circuit breaker load side connection. 
 
   
   
     8. A method in accordance with  claim 6  further comprising:
 measuring a voltage signal across the circuit breaker contact pair; and 
 measuring a current through the circuit breaker contact pair. 
 
   
   
     9. A method in accordance with  claim 8  wherein measuring a voltage signal across the circuit breaker contacts comprises measuring a voltage signal that includes an injected portion and an induced portion. 
   
   
     10. A method in accordance with  claim 8  further comprising determining the resistance of the circuit breaker contact pair using the formula:
     R   n =( V   N −( V   N−1   +V   N+1 )/2)/( I   N −( I   N−1   +I   N+1 )/2); 
 where; 
 R n  is the resistance of at least one of the pre-insertion resistor and the circuit breaker contact pair; 
 V N  is a local minimum magnitude of the injected and induced voltage signal; 
 V N−1  is a local maximum magnitude of the injected and induced voltage signal preceding the local minimum; 
 V N+1  is a local maximum magnitude of the injected and induced voltage signal succeeding the local minimum; 
 I N  is a local minimum magnitude of the injected and induced current signal; 
 I N−1  is a local maximum magnitude of the injected and induced current signal preceding the local minimum; and 
 I N+1  is a local maximum magnitude of the injected and induced current signal succeeding the local minimum. 
 
   
   
     11. A method in accordance with  claim 6  wherein injecting a voltage signal comprises injecting a square wave voltage signal. 
   
   
     12. A method in accordance with  claim 11  wherein injecting a square wave voltage signal comprises injecting a square wave voltage signal wherein the voltage signal varies from about ten volts to about fifty-five volts. 
   
   
     13. A method in accordance with  claim 11  wherein injecting a square wave voltage signal comprises injecting a square wave voltage signal at a voltage signal frequency of about ten kilohertz. 
   
   
     14. A method in accordance with  claim 6  further comprising:
 determining a circuit breaker contact closing time; and 
 determining a circuit breaker contact opening time. 
 
   
   
     15. A computer program embodied on a computer readable media for analyzing circuit breakers comprising a software code segment programmed to:
 inject a voltage signal across a circuit breaker contact pair during a testing sequence; and 
 determine a circuit breaker pre-insertion resistor resistance value using three voltage samples and three corresponding current samples to facilitate reducing an induced current measurement error wherein the samples are spaced apart approximately one half period of the voltage signal. 
 
   
   
     16. A software code segment in accordance with  claim 15  programmed to:
 inject a voltage signal across the circuit breaker contacts; 
 measure a voltage magnitude across the circuit breaker contacts; and 
 measure a current through the circuit breaker contacts. 
 
   
   
     17. A software code segment in accordance with  claim 16  further programmed to inject a square wave voltage signal. 
   
   
     18. A software code segment in accordance with  claim 17  programmed to inject a square wave voltage signal that varies from about ten volts to about fifty-five volts. 
   
   
     19. A software code segment in accordance with  claim 17  programmed to inject a square wave voltage signal that comprises a frequency of about ten kilohertz. 
   
   
     20. A software code segment in accordance with  claim 15  programmed to measure a voltage magnitude across the circuit breaker contacts that includes an injected portion and an induced portion. 
   
   
     21. A software code segment in accordance with  claim 15  further programmed to determine the resistance of the circuit breaker contacts using:
     R   n =( V   N −( V   N−1   +V   N+1 )/2)/( I   N −( I   N−1   +I   N+1 )/2); 
 where; 
 R n  is the resistance of at least one of the pre-insertion resistor and the circuit breaker contacts; 
 V N  is a local minimum magnitude of the injected and induced voltage signal; 
 V N−1  is a local maximum magnitude of the injected and induced voltage signal preceding the local minimum; 
 V N+1  is a local maximum magnitude of the injected and induced voltage signal succeeding the local minimum; 
 I N  is a local minimum magnitude of the injected and induced current signal; 
 I N−1  is a local maximum magnitude of the injected and induced current signal preceding the local minimum; and 
 I N+1  is a local maximum magnitude of the injected and induced current signal succeeding the local minimum. 
 
   
   
     22. A software code segment in accordance with  claim 15  further programmed to:
 determine a circuit breaker contact closing time; and 
 determine a circuit breaker contact opening time. 
 
   
   
     23. A circuit breaker test device for analyzing the operation of circuit breakers comprising:
 a testing circuit electrically coupled to at least one output terminal; and 
 a processor communicatively coupled to said testing circuit, said processor programmed to determine at least one of a circuit breaker contact timing measurement and a circuit breaker contact resistance measurement using a square wave test signal injected across the circuit breaker contact and measuring plurality of voltage values sampled across the circuit breaker contact and corresponding current samples to calculate said circuit breaker contact resistance to facilitate minimizing induced current measurement error wherein the samples are spaced apart approximately one half period of the voltage signal. 
 
   
   
     24. A circuit breaker test device in accordance with  claim 23  wherein an overvoltage protection circuit is electrically coupled between the at least one output terminal and electrical ground. 
   
   
     25. A circuit breaker test device in accordance with  claim 23  wherein said processor is further programmed to determine at least one of a main contact timing measurement and a pre-insertion resistor contact timing measurement. 
   
   
     26. A circuit breaker test device in accordance with  claim 23  wherein said processor is further programmed to determine at least one of a circuit breaker main contact resistance and a circuit breaker pre-insertion resistor resistance. 
   
   
     27. A circuit breaker test device in accordance with  claim 23  wherein said testing circuit comprises:
 a four quadrant voltage source; 
 a current limiting resistor electrically coupled in series with the voltage source; 
 an ammeter electrically coupled in series with the voltage source; and 
 a voltmeter electrically coupled in parallel with the series combination of said voltage source, said current limiting resistor, and said ammeter. 
 
   
   
     28. A circuit breaker test device in accordance with  claim 23  further comprising a grounded case wherein said circuit breaker test device comprises two output terminals and wherein said overvoltage protection circuit comprises a first transient voltage surge suppressor electrically coupled between a first output terminal and said circuit breaker test device case, a second transient voltage surge suppressor electrically coupled between said two output terminals, and a third transient voltage surge suppressor electrically coupled between said second output terminal and said circuit breaker test device case. 
   
   
     29. A circuit breaker test device in accordance with  claim 28  wherein at least one of said transient voltage surge suppressor is a bi-directional transient voltage surge suppressor. 
   
   
     30. A circuit breaker test device in accordance with  claim 23  further comprising a processor communicatively coupled to at least one of said voltage source, said voltmeter, and said ammeter, said processor configured to receive electrical signals from said voltage source, said voltmeter, and said ammeter for monitoring the electrical signals and for transmitting a measurement output. 
   
   
     31. A circuit breaker test device in accordance with  claim 30  wherein said processor is programmed to determine the resistance of the circuit breaker contacts using:
     R   n =( V   N −( V   N−1   +V   N+1 )/2)/( I   N −( I   N−1   +I   N+1 )/2); 
 where; 
 R n  is the resistance of at least one of the pre-insertion resistor and the circuit breaker contacts; 
 V N  is a local minimum magnitude of the injected and induced voltage signal; 
 V N−1  is a local maximum magnitude of the injected and induced voltage signal preceding the local minimum; 
 V N+1  is a local maximum magnitude of the injected and induced voltage signal succeeding the local minimum; 
 I N  is a local minimum magnitude of the injected and induced current signal; 
 I N−1  is a local maximum magnitude of the injected and induced current signal preceding the local minimum; and 
 I N+1  is a local maximum magnitude of the injected and induced current signal succeeding the local minimum.